Federal investigators are probing a private company that conducted a security background check on the source of the National Security Agency leaks, the Wall Street Journal reported Thursday.

USIS, a contractor that performs over two-thirds of the security background checks for the Office of Personnel Management, conducted Edward Snowden's security background investigation in 2011. Sen. Claire McCaskill (D-MO) said at the start of a special Senate hearing that USIS is being probed for a "systematic failure to conduct investigations," according to the Journal.

The probe has not been connected to the background check conducted on Edward Snowden.

Both federal officials and USIS declined to comment on the ongoing investigation.